No abstract

Variation in floral displays, both between and within species, has been long known to be shaped by the mutualistic interactions that plants establish with their pollinators. However, increasing evidence suggests that abiotic selection pressures influence floral diversity as well. Here, we analyse the genetic and environmental factors that underlie patterns of floral pigmentation in wild sunflowers. While sunflower inflorescences appear invariably yellow to the human eye, they display extreme diversity for patterns of ultraviolet pigmentation, which are visible to most pollinators. We show that this diversity is largely controlled by cis-regulatory variation affecting a single MYB transcription factor, HaMYB111, through accumulation of ultraviolet (UV)-absorbing flavonol glycosides in ligules (the ‘petals’ of sunflower inflorescences). Different patterns of ultraviolet pigments in flowers are strongly correlated with pollinator preferences. Furthermore, variation for floral ultraviolet patterns is associated with environmental variables, especially relative humidity, across populations of wild sunflowers. Ligules with larger ultraviolet patterns, which are found in drier environments, show increased resistance to desiccation, suggesting a role in reducing water loss. The dual role of floral UV patterns in pollinator attraction and abiotic response reveals the complex adaptive balance underlying the evolution of floral traits.

Species often include multiple ecotypes that are adapted to different environments. But how do ecotypes arise, and how are their distinctive combinations of adaptive alleles maintained despite hybridization with non-adapted populations? Re-sequencing of 1506 wild sunflowers from three species identified 37 large (1-100 Mbp), non-recombining haplotype blocks associated with numerous ecologically relevant traits, and soil and climate characteristics. Limited recombination in these regions keeps adaptive alleles together, and we find that they differentiate several sunflower ecotypes; for example, they control a 77 day difference in flowering between ecotypes of silverleaf sunflower (likely through deletion of a FLOWERING LOCUS T homolog), and are associated with seed size, flowering time and soil fertility in dune-adapted sunflowers. These haplotypes are highly divergent, associated with polymorphic structural variants, and often appear to represent introgressions from other, possibly extinct, congeners. This work highlights a pervasive role of structural variation in maintaining complex ecotypic adaptation.Local adaptation is common in species that experience different environments across their range.This can result in the formation of ecotypes, ecological races with distinct morphological and/or physiological characteristics that provide an environment-specific fitness advantage. Despite the prevalence of ecotypic differentiation, much remains to be understood about its genetic basis and the evolutionary mechanisms leading to its establishment and maintenance. In particular, a

Patterns of genetic variation in wide-ranging species are a product of multiple processes, including local adaptation, demography, and migration. Since dispersal is limited in most plants, isolation by distance is common (Heywood, 1991;Wright, 1943). In wide-ranging species that span environmental gradients, migration between environmental niches is often reduced due to selection against immigrants (i.e., isolation by environment) (Sexton et al., 2014). This can result in a genome-wide signal of reduced migration, or be restricted to specific genomic regions depending on the strength of selection and the genomic architecture of adaptation. Reduced migration between populations can lead to the development of intraspecific forms that are variously called races, ecotypes, varieties and subspecies. Regardless of taxonomic classification, intraspecific geographic variation represents an important intermediate stage

Even if a web-based messaging service offered confidential channels, how would users know whether their keys, or indeed even their plaintext, was not being exfiltrated? What if a variety of applications offered confidentiality? How would a user gain trust in all of them? In this paper we argue that a platform for private web applications is the only practical way for users to gain assurance about the confidentiality claims of a large number of full-featured web-services.We introduce Beeswax, a client-side platform that allows confidential data to be exchanged between users at the behest of an application, through a narrow set of APIs. Beeswax installs in a modern browser to deliver a complete practical solution, from key distribution to isolation of private data from the applications, thereby making an analysis of application code unnecessary. This focuses scrutiny and trust on the platform itself, rather than on all the applications using it.